Generally as soon as you open up a wall or change the use of a space (i.e. making an unfinished attic, finished) you'll need permits & potentially an architect.  

Here are some details that might help guide advice.Pre-manufactured home built in 1996.Lot size:6000sqftHad full inspections done and passed with flying colors, even structural.Has detached steel 2-car garage structure.ARV:$75-80kSQFT: 1080Beds:3Baths:2Repairs needed: paint on interior walls and wood cabinet paint.

Here are some details that might help guide advice.Pre-manufactured home built in 1996.Lot size:6000sqftHad full inspections done and passed with flying colors, even structural.Has detached steel 2-car garage structure.ARV:$75-80kSQFT: 1080Beds:3Baths:2Repairs needed: paint on interior walls and wood cabinet paint.

Here are some details that might help guide advice.Pre-manufactured home built in 1996.Lot size:6000sqftHad full inspections done and passed with flying colors, even structural.Has detached steel 2-car garage structure.ARV:$75-80kSQFT: 1080Beds:3Baths:2Repairs needed: paint on interior walls and wood cabinet paint.

The NYSE, United Airlines, The Wall Street Journal and BiggerPockets were all attacked and taken down today.

Or common walls share the same cicuits? 

Walls/Ceiling Painted w/ 8ft ceilingsNew front doorKitchen/ Dinning room 259ft^2Wall paper removalNew counter topsAppliances- (fridge, stove-top, oven, range, dishwasher)Replacement Window- 1(3'x3')Walls/Ceiling Painted w/ 8ft ceilingsLaundry room/mud room 180ft^2New flooringWalls/Ceiling Painted w/ 8ft ceilings3/4 bath on 1st floor 100ft^2New flooringNew vanity+sinkWalls/Ceiling Painted w/ 8ft ceilingsInterior Floor 2Bedrooms + Hallway 570ft^2Replacement Windows- 7(2.5'x5'), 1(1.5'x5')Walls/Ceiling Painted w/ 8ft ceilingsCarpet all including stairsFull Bath 2nd Floor 76ft^2New FloorNew vanity+ sinkReplacement Window- 1(2.5'x5')Walls/Ceiling Painted w/ 8ft ceilingsExterior WorkSidingFront and back vinyl- washsides are wood- sand and repaintGarage 1.5 StallCement Siding- Stripe and repaintNew door + mechanicsFront Porch (wood)Repaint wood flooringBack Porch (wood)Re-levelRebuild railingPaint flooring and ceilingBasementMoldNo A/C unitIf someone who rehabs houses could give me a reasonable maximum offer to stay below that would be much help.

I can't seem to find the repair estimate sheet I used, but I remember the total and what I factored in: electrical system replacement, new kitchen, new baths (2), carpet on two levels, demo/drywall basement walls and ceiling, replace HVAC components. 

-Fix Roof-Renovate and re-arrange walls-Redo Electric panel and seal from moisture buildup-Remove tenant (found out she was section 8 but I got lucky and they already found a place!

When you say multifamily do you mean 1-4 unit residential (conjoined walls) or multifamily (5+ units)?